I have a SRAM 10 speed X7 system on a new Trek 29er that came with a 34/11 cassette. As I only ride on the road in a relatively flat location I really only have wind (that is the atmospheric type!) as an issue. I wanted a tighter spread and installed a 27/12, but can't get oll 10 gears to behave. Usually the 24/27 cogs are a lottery. I also have a 28/11 which kind of works, but not perfectly.

I have adjusted the stops and cable tension as prescribed, but suspected the B adjustment was the issue. It certainly made a difference, but it is now all the way out and I still do not think I have the right gap between the idler and cogs.

My agent tells me that the "road" cassette I am using wont work with the MTB drlr' whatever I do - does anyone know if this is true or know of any other tricks that might get me running?

Did you shorten the chain when you installed the cassette? If your chain is too long the jockey wheel cage cannot keep the chain tensioned enough for good shifting.

Until I got my second bicycle, I used 2 wheel sets on my mountain bike one with a 30-11 and one with a 25-12 and used a different length chain with each to keep the jockey pulley tension correct on the rear derailluer. I use a quick link (sram) on my chain to make it easy to remove. you can determine the correct chain length by wrapping the chain snugly around the largest rear sprocket and largest front chainring, without going thru the jockey wheels, and adding 2 complete links (1 set of inner and outer plate = 1 link)

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(04-13-2012, 10:23 PM)barefooter Wrote: Did you shorten the chain when you installed the cassette? If your chain is too long the jockey wheel cage cannot keep the chain tensioned enough for good shifting.

Until I got my second bicycle, I used 2 wheel sets on my mountain bike one with a 30-11 and one with a 25-12 and used a different length chain with each to keep the jockey pulley tension correct on the rear derailluer. I use a quick link (sram) on my chain to make it easy to remove. you can determine the correct chain length by wrapping the chain snugly around the largest rear sprocket and largest front chainring, without going thru the jockey wheels, and adding 2 complete links (1 set of inner and outer plate = 1 link)

Hi Barefooter - good point and I hadn't shortened the length of the chain. However, in my case I am not sure this will have any benefit as I only ride on the middle front rine ring, so the tension should be well within range, but I will give it a try!

Re: compatibility
As SRAM cassettes (at least the MTB ones and I guess also the road) are compatible to Shimano and Shimano road and MTB stuff is compatible to each other I'd guess that SRAM road and MTB cassettes are compatible / interchangeable. At least for Shimano the difference of "road" and "MTB" simply is the available sprocket sizes (and until some years ago the max number of speeds)